1. Field of the Invention
Embodiments of the present invention generally relate to a method of encapsulating a micro-electromechanical system (MEMS) device, and the device formed thereby.
2. Description of the Related Art
Typical MEMS devices are fabricated as stand alone components which are separately packaged, they can then be coupled with separate microcontroller ships to add functionality. More recently there has been a move to couple these MEMS devices onto a complementary metal-oxide semiconductor (CMOS) by building the MEMS elements on separate wafers and then attaching them to CMOS wafers. This manufacturing method is complex and time consuming in that several steps are necessary to ensure that the MEMS devices are properly bolted onto the CMOS wafer and properly sealed to protect the MEMS device from the environment.
In order to address this problem, methods of encapsulating MEMS devices directly onto CMOS wafers using BEOL processes have been developed. Typically, these methods comprise layering a MEMS device between two sacrificial layers and covering the top sacrificial layer with an insulating layer. After the insulating layer is deposited, release holes are created in the insulting layer and a gas etching process is used to remove the sacrificial layers surrounding the MEMS device, thereby defining a cavity in which the MEMS device is contained.
A problem with these methods is that, in order to remove the sacrificial layers, it is necessary to create release holes using complex masking steps. The use of such extra steps increases the overall complexity of the CMOS process and, ultimately, the cost of the resulting device.
Therefore, there is a need for a method of encapsulating MEMS devices in a CMOS BEOL process without having to create release holes in a deposited insulating layer, and devices formed thereby.